The proposed International Study of Schizophrenia is designed to extend the progress achieved in the IPSS by further developing simple and reliable methods for the identification and assessment of psychiatric patients, particularly those suffering from schizophrenia, in different sociocultural settings. It also aims at the development of suitable techniques for the study of the course of schizophrenia and other mental diseases and their natural history and outcome under different socio-economic and cultural conditions. Data obtained about the cohorts of patients identified, assessed and follow-up in a standardized way would serve as the basic material for comparative studies of the influence of sociocultural factors on the course and outcome of psychiatric disorders, and of psychopathology of schizophrenia and other mental disorders. Methods and procedures developed in the study would also be used for intensive studies of social, cultural, psychological and other factors which may cause, precipitate, exacerbate or prevent schizophrenia and other mental disorders.